parallel 0.7.0

Command-line CPU load balancer for executing jobs in parallel
parallel-0.7.0 is not a library.

Parallel: A Command-line CPU Load Balancer Written in Rust

This is an attempt at recreating the functionality of GNU Parallel, a work-stealer for the command-line, in Rust under a MIT license. The end goal will be to support much of the functionality of GNU Parallel and then to extend the functionality further for the next generation of command-line utilities written in Rust. While functionality is important, with the application being developed in Rust, the goal is to also be as fast and efficient as possible.

Note

It's a good idea to install the dash shell as this implementation of Parallel will try to use it by default. Dash is basically a superior implementation of sh that's many times faster and more secure. If dash cannot be found, it will default to sh. Although on Windows it will default to cmd.

See the to-do list for features and improvements that have yet to be done. If you want to contribute, pull requests are welcome. If you have an idea for improvement which isn't listed in the to-do list, feel free to email me and I will consider implementing that idea.

Benchmark Comparison to GNU Parallel

GNU Parallel

~/D/parallel (master) $ seq 1 10000 | time -v /usr/bin/parallel echo > /dev/null
    Command being timed: "/usr/bin/parallel echo"
    User time (seconds): 194.73
    System time (seconds): 66.49
    Percent of CPU this job got: 230%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 1:53.08
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 16140
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 10329017
    Voluntary context switches: 102095
    Involuntary context switches: 229910
    Swaps: 0
    File system inputs: 0
    File system outputs: 0
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

~/D/parallel (master) $ time -v /usr/bin/parallel cat ::: /usr/bin/* > /dev/null
    User time (seconds): 71.71
    System time (seconds): 27.67
    Percent of CPU this job got: 222%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:44.62
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 17576
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 8
    Minor (reclaiming a frame) page faults: 4112045
    Voluntary context switches: 51331
    Involuntary context switches: 101494
    Swaps: 0
    File system inputs: 1512
    File system outputs: 0
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 5

Rust Parallel (Built with MUSL target)

It's highly recommend to compile Parallel with MUSL instead of glibc, as this reduces memory consumption in half and doubles performance.

~/D/parallel (master) $ seq 1 10000 | time -v target/release/x86_64-unknown-linux-musl/parallel echo > /dev/null
    Command being timed: "target/x86_64-unknown-linux-musl/release/parallel echo"
    User time (seconds): 0.55
    System time (seconds): 3.45
    Percent of CPU this job got: 65%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:06.14
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 1768
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 1
    Minor (reclaiming a frame) page faults: 815825
    Voluntary context switches: 72504
    Involuntary context switches: 54392
    Swaps: 0
    File system inputs: 8
    File system outputs: 352
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

~/D/parallel (master) $ time -v target/release/x86_64-unknown-linux-musl/release/parallel cat ::: /usr/bin/* > /dev/null
    User time (seconds): 1.27
    System time (seconds): 5.07
    Percent of CPU this job got: 138%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:04.58
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 1844
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 350701
    Voluntary context switches: 67739
    Involuntary context switches: 44271
    Swaps: 0
    File system inputs: 0
    File system outputs: 480
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

Syntax Examples

The following syntax is supported:

parallel 'echo {}' ::: *                          // {} will be replaced with each input found.
parallel echo ::: *                               // If no placeholders are used, it is automatically assumed.
parallel echo :::: list1 list2 list3              // Read newline-delimited arguments stored in files.
parallel echo ::: arg1 ::::+ list :::+ arg2       // Interchangeably read arguments from the command line and files.
parallel echo ::: 1 2 3 ::: A B C ::: D E F       // Permutate the inputs.
parallel echo {} {1} {2} {3.} ::: 1 2 file.mkv    // {N} tokens are replaced by the Nth input argument
parallel ::: "echo 1" "echo 2" "echo 3"           // If no command is supplied, the input arguments become commands.
parallel 'cd {}; echo Directory: {}; echo - {}'   // Commands may be chained in the platform\'s shell.
ls | parallel 'echo {}'                           // If no input arguments are supplied, stdin will be read.
ls -1 | parallel --pipe cat                       // Piping arguments to the standard input of the given command.

Manual

Parallel parallelizes otherwise non-parallel command-line tasks. When there are a number of commands that need to be executed, which may be executed in parallel, the Parallel application will evenly distribute tasks to all available CPU cores. There are three basic methods for how commands are supplied:

  1. A COMMAND may be defined, followed by an which denotes that all following arguments will be usde as INPUTS for the command.

  2. If no COMMAND is provided, then the INPUTS will be interpreted as COMMANDS.

  3. If no INPUTS are provided, then standard input will be read for INPUTS.

Parallel groups the standard output and error of each child process so that outputs are printed in the order that they are given, as if the tasks were executed serially in a traditional for loop. In addition, commands are executed in the platform's preferred shell by default, which is sh -c on Unix systems, and cmd /C on Windows. This comes at a performance cost, so it can be disabled with the --no-shell option.

INPUT MODES

Input modes are used to determine whether the following inputs are files that contain inputs or inputs themselves. Files with inputs have each input stored on a separate line, and each line is considered an entire input.When there are multiple collected lists of inputs, each individual input list will be permutated together into a single list.

  • :::

Denotes that the input arguments that follow are input arguments. Additionally, those arguments will be collected into a new list.

  • :::+

Denotes that the input arguments that follow are input arguments. Additionally, those arguments will be added to the current list.

  • ::::

Denotes that the input arguments that follow are files with inputs. Additionally, those arguments will be collected into a new list.

  • ::::+

Denotes that the input arguments that follow are files with inputs. Additionally, those arguments will be added to the current list.

INPUT TOKENS

COMMANDs are typically formed the same way that you would normally in the shell, only that you will replace your input arguments with placeholder tokens like {}, {.}, {/}, {//} and {/.}. If no tokens are provided, it is inferred that the final argument in the command will be {}. These tokens will perform text manipulation on the inputs to mangle them in the way you like. Ideas for more tokens are welcome.

  • {}: Each occurrence will be replaced with the name of the input.
  • {.}: Each occurrence will be replaced with the input, with the extension removed.
  • {/}: Each occurrence will be replaced with the base name of the input.
  • {/.}: Each occurrence will be replaced with the base name of the input, with the extension removed.
  • {//}: Each occurrence will be replaced with the directory name of the input.
  • {%}: Each occurrence will be replaced with the slot number.
  • {#}: Each occurrence will be replaced with the job number.
  • {#^}: Each occurrence will be replaced with the total number of jobs.
  • {N}: Where N is a number, display the associated job number.
  • {N.}: will remove the extension from the Nth job.
  • {N/}: Displays the base name (file name) of the Nth job.
  • {N//}: Displays the directory name of the Nth job.
  • {N/.}: Displays the base name of the Nth job with the extension removed.

OPTIONS

Options may also be supplied to the program to change how the program operates:

  • -h, --help: Prints the manual for the application (recommended to pipe it to less).
  • -j, --jobs: Defines the number of jobs/threads to run in parallel.
  • -n, --no-shell: Disables executing commands within the platform's shell for a performance boost.
    • Double quotes and backslashes are used to allow spaces in inputs, similar to standard shells.
  • -p, --pipe: Instead of supplying arguments as arguments to child processes, instead supply the arguments directly to the standard input of each child process.
  • -q, --quote: Retains backslashes that are supplied as the command input.
  • -s, --silent, --quiet: Disables printing the standard output of running processes.
  • --shellquote: Expands upon quote mode by escaping a wide variety of special characters.
  • -v, --verbose: Prints information about running processes.
  • --version: Prints the current version of the application and it's dependencies.
  • --num-cpu-cores: Prints the number of CPU cores in the system and exits.

Useful Examples

Transcoding FLAC music to Opus

ffmpeg is a highly useful application for converting music and videos. However, audio transcoding is limited to a a single core. If you have a large FLAC archive and you wanted to compress it into the efficient Opus codec, it would take forever with the fastest processor to complete, unless you were to take advantage of all cores in your CPU.

parallel 'ffmpeg -v 0 -i "{}" -c:a libopus -b:a 128k "{.}.opus"' ::: $(find -type f -name '*.flac')

Transcoding Videos to VP9

VP9 has one glaring flaw in regards to encoding: it can only use about three cores at any given point in time. If you have an eight core processor and a dozen or more episodes of a TV series to transcode, you can use the parallel program to run three jobs at the same time, provided you also have enough memory for that.

vp9_params="-c:v libvpx-vp9 -tile-columns 6 -frame-parallel 1 -rc_lookahead 25 -threads 4 -speed 1 -b:v 0 -crf 18"
opus_params="-c:a libopus -b:a 128k"
parallel -j 3 'ffmpeg -v 0 -i "{}" $vp9_params $opus_params -f webm "{.}.webm"' ::: $(find -type f -name '*.mkv')

Installation Instructions

There are a number of methods that you can use to install the application. I provide binary packages for AMD64 systems that are available for download:

Gentoo

I have a personal Gentoo layman overlay that provides this application for installation.

Arch Linux

A PKGBUILD is available for Arch Linux users from the AUR.

Everyone Else

rustup component add x86_64-unknown-linux-musl
wget https://github.com/mmstick/parallel/archive/master.zip
unzip master.zip
cd parallel-master
cargo build --release --target x86_64-unknown-linux-musl
sudo install target/x86_64-unknown-linux-musl/release/parallel /usr/local/bin/parallel